1. Field of the Invention
The present invention relates to a method for carrying out a hydrothermal carbonization reaction, in which biomass is supplied to a reaction space, and the reaction conditions required for a hydrothermal carbonization reaction to proceed, with regard to pressure and temperature, are created by blowing in steam, and to a reaction tank for carrying out this method.
2. Description of the Related Art
Such a method and an apparatus for carrying it out are already previously known from the German Offenlegungsschrift [unexamined patent application published for public scrutiny] DE 10 2007 022 840 A1. This method provides that a pre-treatment step is first carried out in a reaction chain, after which the pre-treated biomass, which is pre-heated in this connection, is brought into a reaction space. During transport of the biomass from the pre-heating container to the reaction space, using a conveyor pump, a pressure increase is carried out in this connection. The biomass that has arrived in the reaction space is then subjected to a further pressure increase, in order to create the reaction conditions for hydrothermal carbonization.
The essential process parameters that are required for the hydrothermal carbonization reaction to take place are sufficient pressure, on the order of approximately 25 bar, and a temperature above 180° C., preferably between 210 and 230° C. However, in this connection, the problem exists that the biomass being conveyed into the reaction space has a certain heat capacity, and therefore the outer regions, and then, with a clear delay, the inner regions of the biomass being introduced reach the required reaction parameters, so that the carbonization reaction takes place first on the outside, and takes place on the inside only with a clear delay.
In order to circumvent this, it is known to provide beater-type mixing devices within the reaction space, in order to achieve a uniform distribution or the temperature and the pressure in the biomass. However, this method of procedure accelerates the carbonization reaction or the complete reaction of the entire biomass only to a very slight extent.